The cost-effectiveness core will provide the experience and technical resources to assess cost-effectiveness of the interventions studied or proposed in the Program Project. The CE core will apply the principles of cost-effectiveness analysis, decision modeling, and utility assessment to evaluate the policy implications of changing health beliefs. By providing a unifying paradigm, the CE core will encourage synergies between the component projects by encouraging the adoption of similar data elements, theoretical models, and approaches to design and analysis. The approach to CE analysis includes 6 steps: (1) define the intervention; (2) identify relevant costs; (3) identify relevant effectiveness parameters; (4) measure costs; (5) measure effectiveness; and (6) account for uncertainties. Because trials do not consider all relevant patient populations and do not follow subjects throughout the entire time period of interest, sufficiently comprehensive CE analyses often require extrapolation of future costs and benefits. Decision analysis will be used to make these extrapolations. Decision analysis will also be used to provide normative models; for example, in order to compare current practices regarding estrogen replacement therapy with optimal practices. Utility assessment will provide quantitative representations of patient preferences for health-related outcomes and interventions, as inputs into the calculation of quality-adjusted life years. Members of the CE core have substantial experience in CE analysis, decision modeling, and utility assessment. In addition, the group has practical experience in applying these methodologies in the context of complex multi-disciplinary studies.